A participant in this year's Miss BumBum competition -- a popular contest to find Brazil's best derriere -- this week stunned commuters on São Paulo's famed Paulista Avenue when she hopped on a bus dressed only in a bikini, Tribuna Hoje reported.

The 60-degree weather did not keep Dani Sperle from sporting the attire perhaps more appropriate on the beaches of her hometown of Rio de Janeiro.

"It was an incredible experience," the 33-year-old told the Daily Star about her stroll.

"I was very much appreciated; riding in a bus on Paulista Avenue was more difficult than a nude catwalk," Sperle added.

The traditional Miss BumBum competition, meanwhile, comes with a set of new rules this year after an infection in her buttocks implant had meant months of intensive care for a 2012 contestant. Organizers are now going to great lengths to enforce a ban on surgically improved derrieres, founder Cacau Oliver told Brazil's Diário do Nordeste.

"In past editions (of the contest), we had a rule that said that we would ask for an X-ray exam if there were any suspicions of silicone implants in the buttocks," Oliver said.

"This year, the presentation of clinical exams will be mandatory to avoid that participants have made use of any kind of product," the organizer added.

The measures, required by the American production company set to film the event, are a reaction to the case of 2012 BumBum runner-up Andressa Urach, whose buttock-fillers "rotted" her muscles and had to be removed, according to the Daily Mail. Earlier this year, the 27-year-old had to again undergo emergency surgery to remove substances from her left butt cheek.

"I am suffering a lot, but God is with me," Urach then told the British newspaper. "It's my fault, my vanity made me push the limits. Thanks to God I no longer need my body to work, now I work with honor and can sustain my family like that. I prefer to have legs and be able to walk and lose half a buttock than to die," she added.